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Re: [PATCH 1/3] block: push error reporting into bdrv_all_*_snapshot fun
From: |
Max Reitz |
Subject: |
Re: [PATCH 1/3] block: push error reporting into bdrv_all_*_snapshot functions |
Date: |
Mon, 12 Oct 2020 13:09:59 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 |
On 12.10.20 12:16, Philippe Mathieu-Daudé wrote:
> On 10/12/20 12:07 PM, Max Reitz wrote:
>> On 08.10.20 19:48, Philippe Mathieu-Daudé wrote:
>>> From: Daniel P. Berrangé <berrange@redhat.com>
>>>
>>> The bdrv_all_*_snapshot functions return a BlockDriverState pointer
>>> for the invalid backend, which the callers then use to report an
>>> error message. In some cases multiple callers are reporting the
>>> same error message, but with slightly different text. In the future
>>> there will be more error scenarios for some of these methods, which
>>> will benefit from fine grained error message reporting. So it is
>>> helpful to push error reporting down a level.
>>>
>>> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
>>> ---
>>> include/block/snapshot.h | 14 +++----
>>> block/monitor/block-hmp-cmds.c | 7 ++--
>>> block/snapshot.c | 77 +++++++++++++++++-----------------
>>> migration/savevm.c | 37 +++++-----------
>>> monitor/hmp-cmds.c | 7 +---
>>> replay/replay-debugging.c | 4 +-
>>> tests/qemu-iotests/267.out | 10 ++---
>>> 7 files changed, 67 insertions(+), 89 deletions(-)
>>
>> Looks good overall to me, but for some reason this patch pulls in the
>> @ok and @ret variables from the top scope of all concerned functions
>> into the inner scopes of the BDS loops, and drops their initialization.
>> That’s wrong, because we only call the respective snapshotting
>> functions on some BDSs, so the return value stays uninitialized for all
>> other BDSs:
>
> Indeed, thanks for catching that.
>
> [...]
>>> int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
>>> BlockDriverState *vm_state_bs,
>>> uint64_t vm_state_size,
>>> - BlockDriverState **first_bad_bs)
>>> + Error **errp)
>>> {
>>> - int err = 0;
>>> BlockDriverState *bs;
>>> BdrvNextIterator it;
>>> for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
>>> AioContext *ctx = bdrv_get_aio_context(bs);
>>> + int ret;
>>
>> And one final time.
>>
>> Max
>>
>>> aio_context_acquire(ctx);
>>> if (bs == vm_state_bs) {
>>> sn->vm_state_size = vm_state_size;
>>> - err = bdrv_snapshot_create(bs, sn);
>>> + ret = bdrv_snapshot_create(bs, sn);
>>> } else if (bdrv_all_snapshots_includes_bs(bs)) {
>>> sn->vm_state_size = 0;
>>> - err = bdrv_snapshot_create(bs, sn);
>>> + ret = bdrv_snapshot_create(bs, sn);
>
> This one is not needed.
Why not? Is bdrv_all_snapshots_includes_bs(bs) guaranteed to be true?
(I don’t see any a plain “else” branch, or where ret would be set
outside of these two “if” blocks.)
Max
>>> }
>>> aio_context_release(ctx);
>>> - if (err < 0) {
>>> + if (ret < 0) {
>>> + error_setg(errp, "Could not create snapshot '%s' on '%s'",
>>> + sn->name, bdrv_get_device_or_node_name(bs));
>>> bdrv_next_cleanup(&it);
>>> - goto fail;
>>> + return -1;
>>> }
>>> }
>>
>
[PATCH 3/3] migration: stop returning errno from load_snapshot(), Philippe Mathieu-Daudé, 2020/10/08
[PATCH 2/3] migration: Make save_snapshot() return bool, not 0/-1, Philippe Mathieu-Daudé, 2020/10/08